Pasteurized Milk Lab
Destiney Kopacz
Mrs. Freeman
Chemistry Honors
May
How does the percentage of fat in pasteurized milk (skim, 1%, 2%, whole) affect the mass of curds formed when vinegar is added?
Purpose
The purpose of the experiment was to find out if the amount of fat in milk affected the amount of curds formed in the experiment.
Hypothesis
If the percentage of fat is higher, then more curds will be formed.
Background Research Milk is made of a mixture of substances, casein protein (80%) and whey protein (20%) being the two main applicable elements, that do not separate/settle when left to rest over time. This mixture is called a colloid. When the pH of milk is lowered, it causes these components to separate. Curds are made of solid casein protein particles (alpha, beta, and kappa) (Technology 1-2), formed into groups called casein micelles, which can be disturbed by lemon juice, though it is a weak acid (Isoelectric Precipitation of Proteins: Casein from Milk ). Instead of remaining as one solid mixture …show more content…
The Isoelectric point of milk has a pH of 4.6 (Procedure for Isoelectric Point of Milk: Making Curds & Whey), and the acidity of lemon juice lowers milk’s pH level to the Isoelectric point. This changes the milk’s original negative net charge to a neutral charge, letting intermolecular forces take over (Isoelectric Precipitation of Proteins: Casein from Milk ) and the Casein proteins are drawn together. More casein causes larger masses of curds to form. Though percentage of milk fat has little effect on whether the milk contains casein or not, it can affect the amount of casein left behind (Does Milk Fat Have Casein? ). When fat is skimmed off the top of milk, small amounts of casein will still be attached to the milk fat that is no longer mixed with the milk (Does Milk Fat Have Casein? ). This may also affect the amount of curds
Mrs. Freeman
Chemistry Honors
May
How does the percentage of fat in pasteurized milk (skim, 1%, 2%, whole) affect the mass of curds formed when vinegar is added?
Purpose
The purpose of the experiment was to find out if the amount of fat in milk affected the amount of curds formed in the experiment.
Hypothesis
If the percentage of fat is higher, then more curds will be formed.
Background Research Milk is made of a mixture of substances, casein protein (80%) and whey protein (20%) being the two main applicable elements, that do not separate/settle when left to rest over time. This mixture is called a colloid. When the pH of milk is lowered, it causes these components to separate. Curds are made of solid casein protein particles (alpha, beta, and kappa) (Technology 1-2), formed into groups called casein micelles, which can be disturbed by lemon juice, though it is a weak acid (Isoelectric Precipitation of Proteins: Casein from Milk ). Instead of remaining as one solid mixture …show more content…
The Isoelectric point of milk has a pH of 4.6 (Procedure for Isoelectric Point of Milk: Making Curds & Whey), and the acidity of lemon juice lowers milk’s pH level to the Isoelectric point. This changes the milk’s original negative net charge to a neutral charge, letting intermolecular forces take over (Isoelectric Precipitation of Proteins: Casein from Milk ) and the Casein proteins are drawn together. More casein causes larger masses of curds to form. Though percentage of milk fat has little effect on whether the milk contains casein or not, it can affect the amount of casein left behind (Does Milk Fat Have Casein? ). When fat is skimmed off the top of milk, small amounts of casein will still be attached to the milk fat that is no longer mixed with the milk (Does Milk Fat Have Casein? ). This may also affect the amount of curds